Acoustic-translating device



Jan.

LHEZGAW (II-i. k3. CRUUESE ACOUSTIC TRANSLATING DEVICE Filed Dec. 1922 2SheetS-ShWt l 5; Sheets-$heet 2 G. B. CZROUSE:

ACOUSTIC TRANSLATING DEVICE iled Dec 6 1922 Jam 17, 1928.

AE l" OFFlClil.

U'ELOUEBIE, 01h STAMFORD, UOI l'NH'U'EIC'UT.

ACOUESTIGJPEANSLATING DlllVICE.

Application died December 6, 1922. Serial No. 605,153.

The SLllJjGCll ll'llllJECl of the present application relates to devicesfor translating electrical undulations into sound vibrations and thefeatures of invention hereinafter disclosed are directed toward theimprovement of such apparatus whereby sound vibrations may be faithfullyreproduced.

lllhile certain or all of the features of in vention may be embodied inother forms of devices, within the scope of the appended claims, theymay perhaps best he explained as embodied in a telephone receiver. Ineniployii the term telephone receiver 1 mean to refer to and include notonly reccivers employed in land-line telephony but those employed inradio telephony and telegraphy as Well.

in the receiver now commonly in use in land-line telephony, the motionsof the dia' phragm do not exactly correspond to the changes in currentin the coils and therefore voices heard over land-line telephones do notsound quite natural. In land line telephony the faithfulness ornaturuluess of the voice reproductions is of minor importance so long;as the speech is intelligible. With the advent of radio telegraphy anduse of telephone receivers as a part thereof new requirements wereintroduced but chiefly as to increased sensitivity. In radio telegraphyit is unnecessary that the quality or pitch of the received signals bearany ewctly definite relationship to the undulw ti 15 or transmittedimpulses. However, in radio telephony the now common practice oflu'oadcasting or transmitting music and I peeches has introduced new andmore severe requirements. It is of great in'iportune" that the music orspeech at the transmitting station be faithfully reproduced as toquality as Well as pitch at the receiver or receivers. The metallicdiaphragins heretofore commonly employed in receivers for telephone orradio telegraph signals are open to serious objections when employed inthe reception of music or speech Where faithful reproduction as toquality and pitch are important. @uch a inetr lic dia phrsgni has adefinite natural period of vibration. lt vibrates much more easily atthis pitch than at any other. ll hen a receiver embodying such ametallic diaphragm lfl called upon to respond to undulationsrepresenting a musical sound consisting of a fundamental and certaindefinite overtones or harmonies, any harmonic of the same period as thenatural period of the dia phragm will be emitted with comparativeloudness While the components of other periods will be relativelysuppressed. Thus the quality of the reproduced sound is quite differentfrom the transmitted sound. Furtherir re, When the transmitted sounddoes not comprise a fundamental or har inonic of the same period as thenatural period of such a metallic diaphragm, the latter neverthelesssounds a tone of its natural period thereby changing the quality of thetransmitted sound and quite often changing a transmitted musical tone ortone-co1nbination into noise.

Among other objects the present invention has for one of its mostimportant purposes to reduce and practically eliminate distortion of thetransmitted sound in telephone receivers by providing a diaphragm whichdoes not vibrate freely by itself and has no natural periodtvhich can bedelinitely distinguished. To this end, I pro pose to construct thediaphragm. of such material, or combinations of materials, that there isa comparatively high degree of friction between its molecules. In otherWords, ll propose to provide a diaphragm which has high internaldanuiiing. With this preliminary explanation, ll now refer to thedrawings, wherein I have illustrated certain now preferred physicalembodiments of the invention and in which:

Fig. l is a plan view, with various parts broken away, illustrating apreferred form of receiver embodying certain features of the invention.lg.

Fig. 1 is a fragmentary sectional eleva tion of an instrument similar tothat shown in Figs. 1 to 3 but illustrating a modifica tion.

2 is a sectional elevation taken substantially on the line 2-2 of Fig.1.

3 is a sectional elevation taken substantially on the line 3-3 of idle.1.

Fig. 4t is an elevation showing a modified form of the invention Fig. 5is a plan view (with the dia- (ill tit?

phragm, cap and armature removed) of a modified form of device.

Fig. 6 is a section taken substantially on the line 6-6 of Fig. 5.

Figs. 7 and 8 are respectively a plan view and elevation, on a largerscale, of the diaphragm and armatures shown in Fig. 6.

Fig. 9 is a view similar to Fig. 6 but illustrating a furthermodification.

Fig. 10 is a fragmentary sectional elevation of a further modification;and,

Fig. 11 is a plan View of certain of the elements shown in Fig. 10.

Calling attention to Figs. 1 to 3, it will be seen that I have thereillustrated a watchcase receiver comprising a cup-shaped housing orcasing 10 externally screw-threaded to co-operate with theinternally-threaded ear cap 11 having the central opening 12. A.diaphragm 13 extends across the housing 10 and is adapted to be vibratedby the preferred form of electromagnetic means which I shall nowdescribe.

The diaphragm 13 has secured the eto, by suitable adhesive material,riveting or other securing means, a disc or button 14 of soft iron orother suitable magnetizable material.

. The receiver is provided with the permanent magnet 15, electromagnets17 having cores 0r pole-pieces 16, all of which may be secured to thecasing 10 in the usual way and which may be substantially of the usualconstruction except that the pole tips; i. e., the upper ends of thepoles 16, are preferably bent toward each other as indicated in Figs. 1and 3. The receiver may also be provided with the terminal block 18 andcord-attaching eye-member 19 of common and well-known construction.

The diaphragm 13 is preferably constructed of such material, orcombination of materials, as to provide a diaphragm having acomparatively high degree of friction between its molecules; i. e., acomparatively high degree of internal damping and having no naturalperiod that can readily be distinguished. For example, a diaphragm builtof laminations of paper, cloth, or other fibrous material, impregnatedwith natural or synthetic gum, or other suitable binder, and baked, ifdesired, may be employed. At present I prefer to construct the diaphragm13 of material known in the electrical arts as bakelite-dilecto.

The. efficiency of operation of receivers such as I have described, andin tact other receivers of the same general type, depends on the meanair-gap distance between the poles and armature 1 1. In the practicalconstruction o'l diaphragms such as I have above described it has beenfound extremely diliicult to produce diaphragms which are absolutelystandard as to shape; i. e., some are found to be dished more or less.Therefore, in order to manufacture such receivers at a cost within themeans of the average user, it is extremely important, it not essential,that there be some form of means for adjusting the mean distance betweenthe armature and poles and further, it is important that this means befairly simple. One form or such adjusting means is illustrated in Figs.1 to anl may be constructed substantially as 'follows.

A ring or annulus 20 oi spring metal, or other resilient material, splitat 21 is mounted at the upper end or the casing 10, the upper inner edgeof the casing being bev elled and the outer lower edge of the annulus 20being l cvelled as clearly indicated in Figs. 2 and 3. The diaphragm 1.3is adapted to upon the upper :l'ace ol the ring 20 and to be eng ged bythe annular rib 22 of the cap 11. lly virtue of this construction, whenthe cap 11. is screwed toward the casing the diaphragm 13 and ring 20are moved toward the pole-pieces it, such movement being opposed by theinherent resiliency of the ring 20. llhen the cap 11 is screwed in thereverse direction, the ring 20 expands, and moves outwardly forcing thediaphragm 13 against the seat 22.

Means for holding the cap 1.1 and casing 10 in various relative postions of adjustment are provided. A preferred form 01' such means will.be found illustrated in Figs. 1 and 2 and may be constructedsubstantially as follows. A strip 30 0t bridge-like shape is adapted tobear at its lower end against the inner wall oi the housing 10. Theupper end of the bridge 30 projects through an opening 31 in the housingand is adapted to engage the inner threaded wall of the cap 11. A screw32, which passes through an opening in the housing 10, screw-threzuledlyengages a suitablytapped opening in the bridge or locking piece 210.Ubviou, y the screw 32 may be turned in either of up posite directionsand, when so moved, moves the brid e 30 into looking or release posiionwith respect to the cap 1.1, depeinling upon the direction of rotation.

The manipulation and operation ol? the form 01' invention abovedescribed as applied to a radio telephone receiving apparatus may bedescribed as follow-2. To adj;

seat

Lilli airgap the locking screw S52 is u... crc\ .cd or loosened. The carcap 11 should then he turned in the proper direction until the armature14 snaps against the poles 16, due to magneto-motive-force of theperinamcnt magnet 15. This may readily be detected by the click producedby such snapping ol the arn'iature into engagement with the poles. Theear cap 1]. should then be turned in the opposite direction until thediaphragm it and its armatiuhe 1 linore 1 .\\1-. from tho pole pieces asevidenced by a clicking sound. The exact relative position at which thediaphragm moves away from the pole pieces Ill) his

is the leztst oingep that may be employed Wlljl'lOHl] danger of theorinoture i l sticking or freezing on the pole pieces 16 when loudsounds are received. After the siegep odjiiis'tn'ient has been cilectcdthe screw is turned to more the bridge 30 into locking; position. endthe telephone rogciver n; he connected to the receiving epporstus in theproper manner; i. e, as to polarity of the terminals. By virtue of thecomposition ind properties of the diophrugni 13, above tllfiCllllGtl,and the occurucy oit' adjustment of the sir-gap, the sounts reproducedwill le true lOpl'OtlllehlilllS oi the sounds repred by the electricalunduletions through.

n oot coils.

i l. he understood that two properly connected receivers ouch oi. theterm illrstinted in Figs. 1 to ll would preferably be employed tor ahead set. For it loud speaker only one instrument would he required.Thus in Fig. 4: l have illustrated on instrum nt in all respects similarto thetillusd in l g 2 one 0 except tluit cup fill, of inetztl or othersuitable insteriul, harvinp; o sound simplifying horn 112, connected dfor the 121p ll oi: Figs.

1, con'ipuroti've large sent thron -h the receiver, is the when usi toreceiver er it loud speaker (Fig, 4: rattling Will take piece unless thediaphragm set tor it comjr srstivoly large oh gop. li o ovoid 3 tlinggthe c ill may he turned in the chi ction more ewe from the casing 10until n disoppezu's. tin eighth of e .1

- e tor this purpose. invention is susceptible to modificain serious 1spects, in addition to those tion chore noted, Witl'iout departing trointhe scope defined in the appended claims. Thus, in lliggs. ii to inclusio, l. have lllustrotcd a receiver with o diilerent term of urn .ture midpole tips and l have omitted, in these "e, the oinggop edjust nieunsshown in it?" to .-l. The elements 'll'i", and Elle, end respcc- 1 M. wl 1 is, id, ii, to, 5. The orinzu ll. l iu e to the e c i i soitt irorbent t. trot d in Figs. 6 and 8; i. e., to the .7111 of e hollow trio'lur p" 'in with o. t at 51. The ornuiture 5O the diaphragm by means.lit wi l ilitt the reluctance of the magnetic appreciably increased, duethe l since there practically no t across this joint. The pole tips Ibevelled (see liig. 6) to conform pe oi tire armoturc. Due to the :t theorniuture 530 end the JC les E216, the it riner must he in rotating withrespect to, 1 nd HIT l he operation of the instruoirent shown in Figs. 5to 8 is genera ollllllttl to the instrument illustrated in 1 to d, inthat tlv e permanent inc net passes :1 continuous llui; through one orone poles 216, 50, and the other pole 216, thus on continuous pull onthe diuphrz ll hen an undulating Clll'i t is p through the serially, orotherwise, connected ('OllS 2217, 217, the lid); across the grep iscorrcspondingly Varied to inn rilnzttions to the armature end diaphragmin sccorduncc with the electricsl uhdulotion it should he noted that theform of pole and erinoture construction. shown 3' i i .3 to E; possessesthe following; zid'vuni among others. For at given eilective len"1 oi 5path across the cup, at e r motion dieplirzi in, hinore tl .rc con--tscts N h the pole pieces, is :miiv lnc. "o, :t'or o, iiren relimtuin-oo the iron 0 'e, relntivel c light urniotuie nut is it eed since thethis path through the suture is short. ll'urtherinore, since thearmature eic tends hetwe n the pole pieces, ti rtelittle nuipgneticleoltuge troin pole t to pole tip outside oi? the gop.

In Fig. 9 l have illustrated l'jurtl'ier modification, in which twoorine'iures Will he noted that the pole pieces ere ure not ent overtoward each other but are off as shown, eoch. to cooperate w respondingone of the ltllfilt ;lll'QE-S 'lhe ll 1; path between the two mini. isformed by u member 61, oi iron, s1 bevelled at its opposite nds with theorniutures 'lho member *1 suported in any suitable inf-diner, as meansof u pedestal (5G or": nonunztgnetio n e.- teriul secured to the and toWl'iich pedestzil the member 61 is also secured.

While two orinstures ore employed in the form of the invention illusrated in i9. 9, these ormotures are each spsceo from the center of thedieohrugin so that their Weight is less eiiective in lowering tie periodof the diaphragm. li y piecing the orinuturcs un's'y ohrogni conte fromthe dit i r, the oi, up length 1118, be decreased tor u wen motion ofthe diaphragm, on d this i ctor o it'- cts ot the r loyinen t 'lli ti l

lee

ture 71, 72, 73, 75, 76 that may be substituted for the diaphragm 213and armature shown in Fig. 6. In the forms of invention illustrated inFigs. 1 to 9 inclusive I now prefer to employ diaphragms ofbakelitedilecto. However, diaphragms of other material such as aluminum,or other metal, may be employed in at least some 01": the convstructions illustrated in Figs. 1 to 9 with improved results over theprior art devices. In the form shown in Figs. 10 and 11 the diaphragm 71may be constructed of aluminum, or other suitable material, in the formof a cup whose flange extends between the inner split ring and an outerring 72. The inner ring 75 may be expanded by means of a tapered screw76, adapted to screw into the slit of the inner ring, and since theouter ring 72 is comparatively thin, the entire structure 71, 72, 7 5,may be expanded and the diaphragm thereby stretched. By stretching thediaphragm 71 its natural period may be raised without increasing isweight. Itwill be noted that the outer ring 72 is provided with anoutwardly projectingledge or flange adapted to rest upon the upper edgeof the housing 210 when the elements 71, 72 (armature), 73, 75 and 76are substituted for the armature 50 and diaphragm 213 of the deviceshown in Fig. 6.

Instead of employing the structure illustrated in Figs. 1 to 8 toprovide for the adjustment of the mean air gap, I may employ thatillustrated in Fig. 1". In the last mentioned figure, the diaphragm 13is carried by the cap 11. A nut 400, externally threaded, screws intothe cap 11, the diaphragm 13 being clamped between said gap and nut. Thenut is provided with diametrically opposed notches 101 (one of which isillustrated in Fig. 1) into which a spanner wrench or other suitabletool may be insorted to screw the nut into or out of the cap 11. Byvirtue of this construction, the diaphragm 13 may be readily mounted inor removed from the cap 11. Obviously, by turning the cap 11 in onedirection or the other with respect to the casing 10 the mean positionof the armature 14- with respect to the poles of the magnets may beadjusted at will. Any desired adjustment may be held by devices 30, 31,32, not shown in Fig.1 but illustrated in Figs. 1 to 3.

In addition to the advantages above set forth I wish to point outfurther that by virtue of the improved magnetic circuits disclosedcomparatively large wire may be employed in the windings of the in.uments which reduces likelihood of burnouts, a feature which assumesparticular importance when the instruments are usel in connection withvacuum tube amplifiers.

In accordance with the provisions of the patent statutes, I have hereindescribed the principle of operation of my invention, together with theapparatus which I l-OW con sider to represent the best embodimentsthereof, but I desire to have it understood that the apparatus disclosedis only illustrative and that the invention can he carried out by othermeans. Also, while it is designed to use the various features andelements in the combinations and relations described, some of these maybe altered and others omitted and some of the features of eachmodification may be embodied in the others without interfering with themore general results outlined, and the invention extends to such use.

Bakelite-dilccto is a material made of laminations of paper impregnatedwith bakelite and heated and pressed. Bakelite is a product made by achemical union of phenol and formaldehyde.

lVhat I claim is:

1. A telephone receiver coin n'ising in combination, a cup-shapedhousing, a split annulus oi resilient material mounted on the inner edgeof said housing, said annulus and inner edge being provided withco-acting inclined surfaces, a diaphragm mounted on said annulus, an earcap screw-ll]rcadcdl connected to said housing and adapted to move saiddiaphragm toward said housing upon rotation of said cap with respect tosaid housing, and clcctro-imignetic m nus mounted within said housingfor vibrating said diaphragm.

2. A telephone receiver as set forh in claim 1 in which means areprovided .l'or locking the cap and housing in various relative positionsof adjustment.

A device for translating electrical undulations into sound vibrationsand comprising in combination, a casing having :1 body portion anddetachable cup portion, an electromagnet secured within said casing, adiaphragm extending across said casing, means for adjusting the positionof said diaphragm by relative rotational movement of said cap portionand body portion, and means for releasably locking said cap portion andbody portion in various relative positions of adjustment, said lastmentioned means comprising a lwking member connected to one of saidportions and adapted to engage the other of said portions, and a screwfor moving said locking member into engagement with said last mentionedportion.

4. A device for translating electrical undulations into sound vibrationsand cmnprising in combination, a casing having a body portion anddetachable cap portion. on electromagnet secured within said. casing, adiaphragm extending across said casing, means for adjusting the positionof said diaphragm by relative rotational movement oil? said cap portionand body portion, and

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Inn

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means for releasably looking said cap poi-- iiion and body portion invarious IGiEL'fiVG positions of adjustment, said last mentioned meanscomprising :i bridge-shaped look ng inoinbor adapted to bear at one andagainst said body portion and at its other end against said cap portion,and a manually adjustable screw cooperating; with said body portion. andbricigeohagod looking member for moving the lower into gripping ong;5oinont with said cap portion.

in testimony whereof I hoio'to fl ifiil my signature.

GEORGE B CRUUEBE.

